public class No026 {
    /**
     * 输入两棵二叉树A，B，判断B是不是A的子结构。
     * （ps：我们约定空树不是任意一个树的子结构）
     */
    public class TreeNode {
        int val = 0;
        TreeNode left = null;
        TreeNode right = null;

        public TreeNode(int val) {
            this.val = val;
        }
    }

    public boolean HasSubtree(TreeNode root1, TreeNode root2) {
        if (root1 == null || root2 == null) return false;
        return DoesTree1HaveTree2(root1, root2)
                || DoesTree1HaveTree2(root1.left, root2)
                || DoesTree1HaveTree2(root1.right, root2);
    }

    public boolean DoesTree1HaveTree2(TreeNode root1, TreeNode root2) {
        if (root2 == null) return true;
        if (root1 == null) return false;
        if (root1.val != root2.val) return false;
        return DoesTree1HaveTree2(root1.left, root2.left) && DoesTree1HaveTree2(root1.right, root2.right);
    }


}
